Question: $ { {3} \times \left[\begin{array}{rr}{2} & {-1} \\ {3} & {1} \\ {2} & {3}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{3}\times{2} & {3}\times{-1} \\ {3}\times{3} & {3}\times{1} \\ {3}\times{2} & {3}\times{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{6} & {-3} \\ {9} & {3} \\ {6} & {9}\end{array}\right]}$